US20020091359A1 - Site for access to the inside of a channel, and corresponding cannula - Google Patents

Abstract

A site for access to the inside of a channel (1) comprises a receptacle (2), communicating with the inside of the channel (1), in order to hold a plug (4) made of an elastic material and intended to form a leaktight barrier between the inside of the channel (1) and the outside. The plug (4) has a thickness on a longitudinal axis, an inner surface (5) oriented towards the inside of the channel (1), and an outer surface (6) facing away from the inner surface (5). The plug (4) comprises:

an upper part having the outer surface (6) of the plug (4) as its upper limit and having a cross section corresponding substantially to that of the receptacle (2) so as to cooperate exactly with the receptacle (2), and

a lower part having the inner surface (5) of the plug (4) as its lower limit and having a cross section increasing in two opposite directions perpendicular to the longitudinal axis of the plug (4).

Description

• The subject of the present invention is a device permitting access to the inside of a channel.[0001]
• More particularly, the invention concerns an access site arranged on a channel through which a liquid circulates, from which it is desirable to be able to take samples of liquids, and into which it is desirable, where appropriate, to be able to inject substances. More particularly still, the invention concerns an access site appropriate for channels intended for circulation of liquids which must not be contaminated under any circumstances and whose handling may be difficult. This is the case, for example, with a sterile medical solution which is administered to a patient by infusion via a channel connecting a bag of sterile solution to a needle which is inserted into a vein of the patient. This is also the case with blood circulated outside the body of a patient undergoing extracorporeal treatment of blood by means of an actual blood treatment apparatus (haemodialyser, oxygenator, etc.) which is connected to the patient by means of two channels: a transfer channel through which the blood to be treated is conveyed from the patient to the blood treatment apparatus, and a return channel through which the treated blood is conveyed from the treatment apparatus to the patient.[0002]
• Blood poses a particular problem since it is a potentially contaminating liquid (AIDS, hepatitis B), and it is at present felt that the conventional access sites still used on many channels for extracorporeal circulation of blood (blood lines) do not offer maximum protection to the user.[0003]
• A conventional site for access to the inside of a channel comprises a receptacle communicating with the inside of the channel and holding a plug which is made of an elastic material and is intended to form a leaktight barrier between the inside of the channel and the outside.[0004]
• To withdraw a sample of liquid by means of a site of this type, a syringe is used which is equipped with a metal needle whose end is bevelled in order to facilitate penetration of the needle. The needle is driven through the plug until its point is situated in the channel, the liquid is aspirated into the syringe, and the needle is then removed from the plug, which closes back elastically on the hole generated by the needle.[0005]
• When the liquid withdrawn is blood, the person handling the syringe at all times runs the risk of contracting one of the very serious diseases mentioned above, by accidentally pricking himself/herself with the needle used for the sampling.[0006]
• To eliminate this risk, it has long been proposed to form, in the elastic plug of the access sites, a slit extending the entire thickness of the plug, and to use, in conjunction with such sites, blunt needles, without bevels, in particular made of plastic.[0007]
• However, these previously slotted injection sites pose problems of leaktightness. Outside the times when such a site is in use for sampling or injection, that is to say for most of the time, it is essential that the slit in the plug remains well closed upon itself and does not allow liquid to escape to the outside, in particular when said liquid is under pressure. Moreover, it is essential that the needle and the plug cooperate closely during insertion and removal of a needle to ensure that there is no escape of liquid when using the site.[0008]
• The document WO90/11103 describes an access site comprising a receptacle delimiting a frustoconical recess into which a cylindrical plug is driven with force. The plug is then incised and the edges of the receptacle are folded back on themselves, inwards, in order to exert an axial thrust on the periphery of the plug.[0009]
• The document WO90/11103 also describes a cannula intended to cooperate with this access site, comprising a cylindrical body with an inner canal which does not extend as far as the end of the cannula and which communicates with the outside via three lateral slits opening out near the end of the cannula.[0010]
• It is an object of the invention to make available an access site which remains leaktight in all circumstances, in particular upon introduction and removal of a cannula, even when the liquid in the channel is under pressure.[0011]
• To achieve this object, the invention proposes a site for access to the inside of a channel, comprising a receptacle, communicating with the inside of the channel, in order to hold a plug made of an elastic material and intended to form a leaktight barrier between the inside of the channel and the outside, the plug having a thickness on a longitudinal axis, an inner surface oriented towards the inside of the channel, and an outer surface facing away from the inner surface, and comprising means for promoting penetration, through the plug, of a tube for withdrawal or injection of liquid from/into the channel, characterized in that, before being inserted into the receptacle, the plug comprises:[0012]
• an upper part having the outer surface of the plug as its upper limit and having a cross section corresponding substantially to that of the receptacle so as to cooperate exactly with the receptacle, and[0013]
• a lower part having the inner surface of the plug as its lower limit and having a cross section increasing in two opposite directions perpendicular to the longitudinal axis of the plug.[0014]
• According to one characteristic of the invention, the means for promoting penetration, through the plug, of a tube for withdrawal or injection comprise:[0015]
• an oblong hole extending over part of the thickness of the plug, starting from the outer surface of the plug, substantially along the longitudinal axis of the plug, the oblong hole having a cross section slightly smaller than that of the tube, so that the upper part of the plug cooperates exactly with the tube when the latter is driven into the oblong hole, and[0016]
• a prismatic slit substantially dividing the plug into two halves, over part of the thickness of the plug, starting from the inner surface of the plug, the slit having its maximum opening at the inner surface of the plug and extending perpendicular to the opposite directions of widening of the lower part of the plug, the widening of the lower part of the plug and the spreading of the prismatic slit being dimensioned in such a way that, when the plug is inserted into the receptacle, the two facing surfaces of the prismatic slit are applied elastically against one another.[0017]
• The advantage of the two-part configuration of this plug is that of offering optimum leaktightness irrespective of the conditions of use: the lower part, whose two halves are brought close together by the walls of the receptacle, prevents any escape of liquid to the outside when the access site is not being used. When a cannula is driven into the plug, the upper part of the plug exerts a radial elastic thrust on the cannula, resulting from the complementary nature of the cross section of the oblong hole and the cross section of the cannula, said cross section of the cannula preferably being chosen to be slightly greater than that of the hole; moreover, the lower part of the plug exerts a strong lateral elastic thrust on the cannula, resulting from the two halves of the lower part of the plug being forced together by the walls of the receptacle.[0018]
• Another object of the invention is to provide a cannula intended to cooperate with an access site, permitting optimum transfer of liquid during sampling or injection.[0019]
• To achieve this object, a cannula comprises:[0020]
• a tube having an end situated inside the channel when the cannula is driven through the site, and[0021]
• means for preventing the end of the tube from coming into contact with an inner wall of the channel when the cannula is driven through the site.[0022]
• By virtue of this design, the penetration of the cannula into the channel is limited in such a way that the sampling of liquid via the cannula cannot be impeded by the proximity of the end of the cannula to the wall of the channel.[0023]
• Other characteristics and advantages of the invention will become clear on reading the description which follows.[0024]
• Reference will be made to the drawings, in which:[0025]
• FIG. 1 is a cross-sectional view of an injection site on a plane containing the longitudinal axis of the site and the longitudinal axis of the channel on which the site is arranged;[0026]
• FIG. 2 is a cross-sectional view of an injection site plug, before its insertion into the receptacle of the site, on a plane containing the longitudinal axis of the plug;[0027]
• FIG. 3 is a plan view of an injection site plug, before its insertion into the receptacle of the site;[0028]
• FIG. 4 is a perspective view of an injection site plug, before its insertion into the receptacle of the site, in which figure the outer surface of the plug can be seen;[0029]
• FIG. 5 is a perspective view of an injection site plug, before its insertion into the receptacle of the site, in which figure the inner surface of the plug can be seen;[0030]
• FIG. 6[0031]ais a cross-sectional view of a cannula presented in line with the injection site from FIG. 1, on a plane containing the longitudinal axis of the cannula; FIG. 6bis a cross-sectional view along the line A-A through the upper part of the plug; FIG. 6cis a cross-sectional view along the line B-B through the lower part of the plug;
• FIG. 7[0032]ais a cross-sectional view of a cannula driven into the injection site from FIG. 1, on a plane containing the longitudinal axis of the cannula; FIG. 7bis a cross-sectional view along the line A-A through the upper part of the plug; FIG. 7cis a cross-sectional view along the line B-B through the lower part of the plug.
• A site for access to the inside of a channel[0033]1 having a longitudinal axis X comprises areceptacle2 with a tubular wall having a longitudinal axis Y perpendicular to the longitudinal axis X of the channel1. Thereceptacle2 communicates with the channel1 via acircular opening3 centered on the axis Y and formed in the wall of the channel1. Thereceptacle2 is designed to hold aplug4 made of an elastic material (elastomer, for example) and intended to form a leaktight barrier between the inside of the channel1 and the outside. Theplug4 has a thickness on the longitudinal axis Y (in FIG. 1 this thickness is approximately equal to three quarters the diameter of the plug). Theplug4 has aninner surface5 oriented towards the inside of the channel1, and anouter surface6 facing away from the inner surface.
• According to the invention, before its insertion into the[0034]receptacle2, theplug4 has anupper part41 and alower part42. Theouter surface6 of theplug4 forms the upper limit of theupper part41, which has a cross section slightly greater than that of thereceptacle2 in order to cooperate exactly with thereceptacle2 when the plug is driven into thereceptacle2. Theinner surface5 of theplug4 forms the lower limit of thelower part42, which has a cross section increasing, approaching theinner surface5, in two opposite directions perpendicular to the longitudinal axis of theplug4.
• The[0035]plug4 also comprises means for promoting penetration, through theplug4, of a tube for taking a sample of liquid from the channel1 or for injecting liquid into the channel1. According to the invention, these means comprise:
• An[0036]oblong hole7 extending over part of the thickness of theplug4, starting from theouter surface6. Theoblong hole7 has a cylindrical upper portion and a frustoconical lower portion and it opens out on the upper surface with slight widening (chamfer8). The longitudinal axis of thehole7 coincides with the longitudinal axis of theplug4. The cross section of thecylindrical hole7 is slightly smaller than that of a tube for sampling or injection of liquid, so that the upper part of the plug cooperates exactly with thetube21 when the latter is driven into the cylindrical hole7 (see FIG. 7b).
• A[0037]prismatic slit9 which substantially divides theplug4 into two halves, over part of the thickness of theplug4, starting from theinner surface5 of theplug4. The maximum opening of theslit9 is situated on theinner surface5 of theplug4, and itsapex10 intersects the longitudinal axis of theplug4 on the perpendicular. The general direction of theprismatic slit9 is perpendicular to the opposite directions of widening of the lower part of theplug4. The widening of thelower part42 of theplug4 and the spreading of theprismatic slit9 are dimensioned in such a way that when theplug4 is driven into thereceptacle2, the walls of thereceptacle2 apply the two halves of thelower part42 of theplug4 firmly against each other and hermetically seal the slit9 (see FIG. 6c).
• The access site which has just been described is designed to cooperate with a[0038]cannula20 comprising acylindrical tube21 attached to a joiningpiece22 for connection of thecannula20 to a syringe. As has been mentioned above, the cross section of thetube21 is slightly greater than the cross section of thehole7 which passes through the upper part of theplug4. According to the invention, thecannula20 is equipped withmeans23 for limiting the engagement of thetube21 in the channel1 so that, when thecannula20 is driven to the maximum into the access site, the end of thetube21 does not come into contact with the wall of the channel1 and therefore cannot be obstructed. In the embodiment shown, the means for limiting the engagement of thetube21 in the channel1 are made up of aflange23 in the form of a disc perpendicular to the axis of thetube21 and fixed to thetube21 in proximity to the joiningpiece22. In other words, the length of thetube21, from theflange23 to the end of thetube21, is equal to the thickness of theplug4 augmented by a distance less than the diameter of the channel1 (in the figure this distance is substantially equal to half the diameter of the channel1).
• All the elements of the[0039]cannula20 are made in one piece from molded plastic (polycarbonate, for example).
• When a sample of liquid is to be taken from a channel equipped with an access site such as that which has just been described, the[0040]cannula20 is fitted on a syringe, then the end of thetube21 is driven into thehole7 of the upper part of theplug4. In this part, theplug4 tightly matches thetube21, on which it exerts a radial elastic thrust, and forms, with thetube21, a leaktight seal preventing any escape of liquid (see FIG. 7b). When the end of thetube21 reaches the lower part of the plug, it spreads apart theslit9 and separates the two halves of theplug4 along a narrow longitudinal strip slightly wider than the diameter of the tube21 (see FIG. 7c). As one continues to push thecannula20 in the direction of thechannel21, the end of thetube21 emerges from theinner surface5 of theplug4, passes through theopening3 of the channel1, and is immobilized approximately on the longitudinal axis X of the channel1 when theflange23 comes into abutment on theupper surface6 of the plug4 (FIG. 7a). In this position of the end of thecannula20, sampling of liquid from the channel1 cannot under any circumstances be obstructed by the wall of the channel1. Upon withdrawal of thecannula20, theslit9 closes progressively until the end of thetube21 reaches the bottom of thehole7, at which moment the two lower halves of theplug4 are again completely joining and form a leaktight barrier between the inside of the channel1 and the bottom of thehole7.
• The invention is not limited to the embodiment which has just been described and variations are possible.[0041]
• Depending on the nature of the channel, the site can be fitted on the channel at various angles (90° in the figures), and it can even be arranged, if appropriate, at the end of a channel.[0042]
• Likewise, the receptacle of the access site does not have to be cylindrical and it can have a cross section of various forms, in particularly oval or elliptic. The same applies to the plug, the shape of which must correspond substantially to that of the receptacle.[0043]
• Finally, the cross section of the hole does not have to be constant, nor does it have to be circular; for example it can be oval, elliptic or almond-shaped. The same applies to the cross section of the tube of the cannula, which must correspond substantially to that of the hole opening out on the upper surface of the plug.[0044]

Claims (6)

1. Site for access to the inside of a channel (1) comprising a receptacle (2), communicating with the inside of the channel (1), in order to hold a plug (4) made of an elastic material and intended to form a leaktight barrier between the inside of the channel (1) and the outside, the plug (4) having a thickness on a longitudinal axis, an inner surface (5) oriented towards the inside of the channel (1), and an outer surface (6) facing away from the inner surface (5), and comprising means for promoting penetration, through the plug (4), of a tube (21) for withdrawal or injection of liquid from/into the channel (1),

characterized in that, before being inserted into the receptacle (2), the plug (4) comprises:

an upper part having the outer surface (6) of the plug (4) as its upper limit and having a cross section corresponding substantially to that of the receptacle (2) so as to cooperate exactly with the receptacle (2), and

a lower part having the inner surface (5) of the plug (4) as its lower limit and having a cross section increasing in two opposite directions perpendicular to the longitudinal axis of the plug (4).

2. Access site according toclaim 1, characterized in that the means for promoting penetration, through the plug (4), of a tube (21) for withdrawal or injection comprise:

an oblong hole (7) extending over part of the thickness of the plug (4), starting from the outer surface (6) of the plug (4), substantially along the longitudinal axis of the plug (4), the oblong hole (7) having a cross section slightly smaller than that of the tube (21), so that the upper part of the plug (4) cooperates exactly with the tube (21) when the latter is driven into the oblong hole (7), and

a prismatic slit (9) substantially dividing the plug (4) into two halves, over part of the thickness of the plug (4), starting from the inner surface (5) of the plug (4), the slit (9) having its maximum opening at the inner surface (5) of the plug (4) and extending perpendicular to the opposite directions of widening of the lower part of the plug (4), the widening of the lower part of the plug (4) and the spreading of the prismatic slit (9) being dimensioned in such a way that when the plug (4) is inserted into the receptacle (2), the two facing surfaces of the prismatic slit (9) are applied elastically against one another.

3. Cannula (20) for cooperating with an access site according toclaim 1, characterized in that it comprises a tube (21), for withdrawal and injection of liquid, having a cross section slightly greater than that of the oblong hole (7) of the plug (4), so that the upper part of the plug (4) cooperates exactly with the tube (21) when the latter is driven into the oblong hole (7).

4. Cannula (20) according toclaim 3, characterized in that it comprises means for preventing the end of the tube (21) from coming into contact with an inner wall of the channel (1) when the cannula (20) is driven through the site.

5. Cannula (20) according toclaim 4, characterized in that the means for preventing the end of the tube (21) from coming into contact with an inner wall of the channel (1) comprise a flange (23) extending substantially perpendicular to the tube (21) so as to come into abutment against the outer surface (6) of the plug (4).

6. Cannula (20) for cooperating with a site for access to the inside of a channel (1) comprising a receptacle (2), communicating with the inside of the channel (1), in order to hold a plug (4) made of an elastic material and intended to form a leaktight barrier between the inside of the channel (1) and the outside, the plug (4) having a longitudinal axis forming an angle with a longitudinal axis of the channel (1), an inner surface (5) oriented towards the inside of the channel (1), and an outer surface (6) facing away from the inner surface (5), and comprising means for promoting penetration, through the plug (4), of a tube (21) for withdrawal or injection of liquid from/into the channel (1), the cannula (20) comprising:

a tube (21) having an end situated inside the channel (1) when the cannula (20) is driven through the site, and

means for preventing the end of the tube (21) from coming into contact with an inner wall of the channel (1) when the cannula (20) is driven through the site.

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